AME 436

P-V & T-s diagrams for ideal Diesel cycle"
Work is done during both 4 → 5 AND 3 → 4 (const. P combustion,
volume increasing, thus w 3→4 = P 3 (v 4 - v 3 )
Ambient intake pressure case shown (no pumping loop)
Pressure (atm)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Compression Combustion Expansion
Blowdown Intake Exhaust
Intake start 1 2
3 4 5
6 7
P-V diagram
0.0
0.E+00 1.E-04 2.E-04 3.E-04 4.E-04 5.E-04 6.E-04
Cylinder volume (m^3)
Temperature (K)
Compression Combustion Expansion
Blowdown Intake Exhaust
Close T-s cycle 1 2
3 4 5
6 7
1000
900 T-s diagram
800
700
600
500
400
300
200
100
0
-200 0 200 400 600 800
Entropy (J/kg-K)
AME 436 - Lecture 8 - Spring 2013 - Ideal cycle analysis
25
Diesel cycle analysis"
Thermal efficiency (ideal cycle, no throttling or friction loss)
work out + work in
" th
= = C (T # T ) + P (v # v ) + C (T # T )
v 4 5 4 4 3 v 2 3
heat in
C P
(T 4
# T 3
)
= (T 4 # T 5 ) + (R /C v )(T 4 # T 3 ) # (T 3 # T 2 )
(C P
/C v
)(T 4
# T 3
)
=1# 1 $ + T 4 (1# (V 5 /V 4 )#($ #1) ) # T 3
(1# (V 2
/V 3
) #($ #1) )
$(T 4
# T 3
)
=1# 1 $ + 1 $ + T 4 (#(V 5 /V 4 )#($ #1) ) + T 3
((V 2
/V 3
) #($ #1) )
$(T 4
# T 3
)
=1+ #T 4
([(V 5
/V 3
)(V 3
/V 4
)] #($ #1) ) + T 3
((V 2
/V 3
) #($ #1) )
$(T 4
# T 3
)
=1+ #T 4
([r /%] #($ #1) ) + T 3
(r #($ #1) )
$(T 4
# T 3
)
= $ #1 + T (1# T /T ) # T (1# T /T )
4 5 4 3 2 3
$
$(T 4
# T 3
)
=1+ #%T 3([r /%] #($ #1) ) + T 3
(r #($ #1) )
$(%T 3
# T 3
)
=1# %([r /%]#($ #1) ) # (r #($ #1) )
=1# 1 % $ #1
$(% #1)
r $ #1 $(% #1)
AME 436 - Lecture 8 - Spring 2013 - Ideal cycle analysis
26
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